Space Physics Flashcards
The earth
The earth is a planet that rotates on its axis which is tilted once in approximately 24 hours
This creates day and night
Day is experienced by the half of the Earth’s surface that is facing the Sun
Night is the other half of the Earth’s surface, facing away from the Sun
The Earth orbits the Sun once in approximately 365 days
This is 1 year
Due to the tilt of the earth this creates season the light rays from the sun have to travel different distances the less distance it has to travel the hotter it is (summer)
The moon
The Moon is a natural satellite around the Earth
It travels around the Earth in roughly a circular orbit once a month
This takes 27-28 days (one month)
The Moon shines with reflected light from the Sun, it does not produce its own light
This means you can not see the full moon at some points creating phrases
Orbital speed
When planets move around the Sun, or a moon moves around a planet, they orbit in circular motion
This means that in one orbit, a planet travels a distance equal to the circumference of a circle
Therefore the equation is 2πr / T = v
R = orbital radius (m)
T = how long it takes for an object to complete finish one orbit (sec) (orbital period)
V = orbital speed
(Kinda like the s = d/t)
Orbital radius = height of the orbit + the radius of whatever its orbiting
The solar system
The sun (centre)
- has 99% of the mass in the solar system thats why it has its own gravitional pull keeping planets in place
Eight planets
- Mercury, Venus, Earth, Mars, (4 small rocky planets)
- Jupiter, Saturn, Uranus, Neptune (4 gaseous and larger planets)
Natural satellites
- eg: moons
artificial satellites
- man made things that orbit an object in space
Dwarf planets
Asteroids and comets
- Asteroids and comets also orbit the sun
-The asteroid belt lies between Mars and Jupiter and one outside Uranus
Accretion model of solar system
The Sun was thought to have formed when gravitational attraction pulled together clouds of hydrogen dust and gas (called nebulae)
Gravity collapsed the matter from the nebula in on itself causing it to spin around the Sun faster and faster
When this is happening it attracts lots of gas (hydrogen) into the centre of the nebulae this causes lots of collisions of the hydrogen atoms causing them to become hotter and hotter as the pressure and the gravitational pull increases (this is called nuclear fusion)
This forms a protostar
When nuclear fusion happens it produces a lot of outward heat this “combats” the gravitational pull and once these forces balance out it becomes stable
The outer gas around the star is still spinning this causes collisions of other elements causing them to stick together, and they become bigger because they form a gravitational pull which pulls EVEN more materials and they form what is called protoplanets
Solar winds that come out of the star push away the lighter elements, this is why there are gassy giants further away from the sun and small and rocky planets closer to the sun
Light speed, light years
Time = distance / speed
Speed being 3 x 10^8 m/s (speed of light)
Light year - the distance travelled in the vacumm of space by light in one year
One light year = 9.5 x 10^15
Elliptical orbits
Orbits of planets, minor planets and comets are elliptical
However, the Sun is not at the centre of an elliptical orbit
This is only the case when the orbit is approximately circular
An object in an elliptical orbit travels faster when closer to the sun
this is because when the object is closer to the sun the gravitational pull is stronger so it gains kinetic energy Causing it to speed up
When the object moves further away from the sun it gains more gravitational potential energy and loses the kinetic energy causing it to slow down
Therefore a stable orbit is formed
The sun
The Sun is a medium sized star consisting of mainly hydrogen and helium
It radiates most of its energy in the infrared, visible and ultraviolet regions of the electromagnetic spectrum
In the centre of a stable star, hydrogen atoms undergo nuclear fusion to form helium releasing a lot of energy
Life cycle of a star (first part)
Forms a stable star see accretion model
Once a star runs out of fuel depending on the mass, if its a medium star it forms a red giant, when it runs out of fuel the gravitational force inwards becomes more than the heat outwards (since its running out of fuel) so the star collapses
When the star collapses the helium starts to react so heavier elements will start to fuse causing it to expand even more eating serval planets
And THAT eventually runs out and now there is a lot of remaining dusts in the solar system called a planetary nebula and since it now cant do lots any more fusion the gravitational force is at its max and heavy matter is pushed into the centre and now it is a white dwarf
A white dwarf gives of some light and heat but eventually that runs out and it becomes a black dwarf which is just a sad rock
If its a larger star then it makes red super giant and when the super giant collapses it starts to fuse heavier elements which causes it to be super unstable and explode making a supernova, heavy elements are scattered around space
If the super nova is very heavy, it produces very strong gravitational forces which pull in foreign objects (a black hole)
But it can form a neutron star in the centre if the mass isnt as heavy this happens when the protons and the electrons fuse together due to the strong gravitational forces to make neutrons
Universe, red shift and CMBR
Milky Way is one of many billions of galaxies making up the Universe and that the diameter of the Milky Way is approximately 100 000 light-years
The universe is constantly expanding one of the ways that proves this is red shift, the wave length from the electromagnetic spectrum is constant getting longer therefore the stars are getting further away from us which means that the universe is constantly expanding, its called red light because red is the longest wavelength in white light (visible light)
There is also another theory, there is lots of CMBR which means cosmic microwave background a microwave raft ion of a specific frequency that is obverse’s in any point in space, we think that it happened during the Big Bang but with a much shorter wavelength (like gamma rays or smth), so when the universe expands the wave because longer and longer so it became microwaves
Hubbles constant, the speed at which a galaxy is moving away from earth in relation to its distance from earth, we can use this to find out the rate of the universe expanding
H = v/d
You can get v (velocity) from using redshift calculations however no need to learn
D is the distance of a far away galaxy and it is found by measuring the brightness of that galaxy
Hubble constant = 2.2 x 10^8 per sec
1/h = d/v = represents the age of the universe
Planetary data, keywords
Orbital distance - average distance between a body and the sun
Orbital duration/period - time taken to complete one orbit
Density - mass per unit volume
Surface temperature - temperature on the surface of the planet
Gravitational field strength - force per unit mass (Neptune has a higher mass than earth because it has a higher gravitational field strength)
Therefore the strength of the gravitational field depends on the mass of the plant because g = w/m
Since the sun has the most mass in the solar system it has the most gravitational pull therefore planets orbit it
The strength of the gravitational field around a planet decreases as the distance increases (when u move away from earth you wont feel the gravitational pull as much)
Orbital speed of the planet decreases as the distance from the sun increases
(Mercury zooms around the sun)
